1. Field of the Invention
The present invention relates to the esterification of hydroxybenzoic acids, and, more especially, relates to the esterification of salicylic acid and parahydroxybenzoic acid.
2. Description of the Prior Art
One conventional technique in this art for preparing esters of hydroxybenzoic acids comprises reacting hydroxybenzoic acid with a halogenated compound, particularly an alkyl halide, in a biphasic medium in the presence of a strong base.
A major disadvantage of this procedure is that several secondary competing reactions are also carried out, resulting in a decrease in yield, particularly competing reactions between the esterification of the carboxyl function and the O-alkylation reaction of the hydroxy function borne by the aromatic ring.
This results in a reduction in the yield of the ester by virtue of the formation of by-products.
Moreover, the conditions of the reaction result in hydrolysis of the halide employed, forming an alcohol in the aqueous phase which necessarily must be subsequently removed. Therefore, a loss in the amount of such halide also ensues.